MDL-78346 tool_langimport: Prevent uninstallation of invalid targets

admin/tool/langimport/classes/controller.php

@@ -112,6 +112,18 @@ public function install_languagepacks($langs, $updating = false) {
     public function uninstall_language($lang) {
         global $CFG;
 
+        $lang = clean_param($lang, PARAM_LANG);
+        if ($lang === '') {
+            // Do not allow uninstallation of invalid languages.
+            // Note: PARAM_LANG returns an empty string for invalid validation.
+            return false;
+        }
+
+        if ($lang === 'en') {
+            // Never allow removal of the default langauge.
+            return false;
+        }
+
         $dest1 = $CFG->dataroot.'/lang/'.$lang;
         $dest2 = $CFG->dirroot.'/lang/'.$lang;
         $rm1 = false;

admin/tool/langimport/index.php

@@ -43,6 +43,13 @@
 $confirmtounistall  = optional_param('confirmtouninstall', '', PARAM_SAFEPATH);  // uninstallation confirmation
 $purgecaches        = optional_param('purgecaches', false, PARAM_BOOL);  // explicit caches reset
 
+// Filter the uninstall language list.
+// If the list contains a language which is not installed, it is replaced with an empty string.
+// When we try to uninstall an empty string, we uninstall every language.
+$uninstalllang = array_filter($uninstalllang, function($lang) {
+    return !empty($lang);
+});
+
 if ($purgecaches) {
     require_sesskey();
     get_string_manager()->reset_caches();

admin/tool/langimport/tests/controller_test.php

@@ -0,0 +1,59 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace tool_langimport;
+
+/**
+ * Tests for \tool_langimport\locale class.
+ *
+ * @package    tool_langimport
+ * @category   test
+ * @coversDefaultClass \tool_langimport\controller
+ * @copyright  2023 Andrew Lyons <andrew@nicols.co.uk>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class controller_test extends \advanced_testcase {
+
+    /**
+     * Test uninstall of language with invalid values.
+     *
+     * @covers ::uninstall_lang
+     * @dataProvider uninstall_lang_invalid_provider
+     * @params string $lang
+     */
+    public function test_uninstall_lang_invalid(string $lang): void {
+        global $CFG;
+
+        $controller = new controller();
+        $this->assertFalse($controller->uninstall_language($lang));
+        $this->assertFileExists("{$CFG->dataroot}/lang");
+        $this->assertFileExists("{$CFG->dirroot}/lang/en");
+    }
+
+    /**
+     * Data provider for uninstall_lang tests with invalid values.
+     *
+     * @return array
+     */
+    public function uninstall_lang_invalid_provider(): array {
+        return [
+            'Empty string' => [''],
+            'Meaningless empty string' => [' '],
+            'Default language' => ['en'],
+            'Invalid language string' => ['swedish'],
+        ];
+    }
+}